Thermal surgical procedures, wherein thermal energy is either withdrawn from and/or delivered to a localized region of biological material in an effort to destroy the region of biological material, are known in the art and have been shown to be an effective treatment of disease, particularly in instances wherein a patient is unwilling or unable to undergo another form of surgery. A thermal surgical procedure may include, for example, a cryosurgical procedure in which thermal energy is removed from biological material to cool and/or freeze the biological material in an effort to destroy it. Such procedures have been routinely used to treat malignancies on the surface of the body and is also used for treating and managing malignancies of internal organs, such as kidney and prostate. Also, a thermal surgical procedure can include a procedure in which thermal energy is added to biological material to heat the biological material in an effort to destroy it. The destruction of biological material may or may not result in ablation of some or all of the biological material. Thermal surgical procedures are useful in treating diseases of various tissues, including, for example, carcinomas of the liver, kidney, and prostate. These techniques are advantageous in that they have the potential for less invasiveness and lower morbidity as compared with surgical excision.
Thermal surgical procedures involving delivery of thermal energy to increase the local temperature of biological material above the physiological temperature is known to be an effective treatment for eliminating malignant tissue. Typical temperatures for thermal surgical procedures involving the delivery of thermal energy are at or above 50 degrees Celsius (° C.). Typically, the biological material is heated to elevated temperatures and is maintained at these temperatures for an interval of several minutes.
Additionally, it is known in the art that freezing biological materials is an effective method for controlling and destroying the cells and tissues of, for example carcinomas of various tissues and organs. Cryosurgical techniques, in combination with monitoring techniques, such as ultrasound and MRI, have provided effective treatment of a number of internal organs, including liver, prostate, and kidneys. Results of cryosurgery involving carcinomas in kidneys suggest that this may prove a useful technique, particularly for small renal cell carcinomas. Cryosurgical procedures typically reduce the temperature of the biological material to temperatures close to or below the temperature at which the biological material will freeze, often below 0° C. and as low as −20 to −60° C. Typically the biological material is cooled to and maintained at these temperatures for an interval of minutes.
Nonetheless, there exists clinical evidence of recurrence of disease in thermal surgically treated patients. This result may be due to the initial challenge of treating the entire diseased tissue. For example, in current thermal surgical procedures it is prudent to take a sufficient surgical margin around diseased tissue to ensure all of the malignant tissue is removed or destroyed. This often involves freezing or heating beyond a tumor and invading surrounding normal tissue. However, care must be taken to not invade too far beyond the diseased tissues, particularly when treating biological material near healthy sensitive tissues. In particular, when treating prostate cancers, which occur principally in the peripheral zone of the prostate near a number of sensitive structures, such as the rectum, bladder, external sphincter, and the cavernosal nerves, a surgeon must be careful to spare the surrounding tissues from injury. This is particularly important in treating the prostate where overfreezing into the areas of the rectum and urethra can cause rectal and urethral fistulas. On the other hand, if a surgeon is too conservative and underheats or underfreezes affected tissues, the disease may not be effectively treated and the likelihood of recurrence of the disease increases.
There is a need in the art, therefore, to improve the clinical application of thermal surgical procedures, including effectively monitoring of the heating or freezing of the biological material to more effectively predict the zone of injury, reproducibly creating and enhancing cell death within the heat treated area or the cryolesion, and improving definition of the edge of the heat treated area or the cryolesion to improve the effectiveness of the kill zone while protecting adjacent normal tissues.